Question: Solve for $x$ and $y$ using substitution. ${4x+2y = -8}$ ${x = -2y+7}$
Since $x$ has already been solved for, substitute $-2y+7$ for $x$ in the first equation. ${4}{(-2y+7)}{+ 2y = -8}$ Simplify and solve for $y$ $-8y+28 + 2y = -8$ $-6y+28 = -8$ $-6y+28{-28} = -8{-28}$ $-6y = -36$ $\dfrac{-6y}{{-6}} = \dfrac{-36}{{-6}}$ ${y = 6}$ Now that you know ${y = 6}$ , plug it back into $\thinspace {x = -2y+7}\thinspace$ to find $x$ ${x = -2}{(6)}{ + 7}$ $x = -12 + 7$ ${x = -5}$ You can also plug ${y = 6}$ into $\thinspace {4x+2y = -8}\thinspace$ and get the same answer for $x$ : ${4x + 2}{(6)}{= -8}$ ${x = -5}$